1. Field of the Invention
The present invention relates to a recording apparatus such as a magnetic recording apparatus or an optical recording apparatus, each having airbearing head sliders (hereinafter simply referred to as a head slider) which is flexibly suspended by a suspension mechanism, carrying a magnetic or an optical transducer over a rotating disk with a constant spacing therebetween. Particularly, it relates to an improvement in a spring member of the suspension mechanism, usually referred to as a gimbal spring, for flexibly mounting the head slider on a load beam of the suspension mechanism.
2. Description of the Related Arts
As is widely known, in a magnetic or an optical recording apparatus, a magnetic or an optical transducer is carried by a head slider which is suspended by a suspension mechanism fixed to a rigid arm of a head positioner such that the may be controllably transferred over a rotating magnetic disk to access a target track of the disk. This is referred to as a seek operation, and the direction in which the head slider is transferred is referred to as a seek direction. Naturally, the seek direction is taken in a substantially radial direction of the relevant magnetic disk. The suspension mechanism comprises a head slider, a load beam and a gimbal spring. The head slider is mounted through the gimbal spring on the free end portion of the load beam which is secured to a rigid arm of the related head positioner at the other end portion.
Before proceeding further, a brief survey is provided regarding various types of relative arrangement between the head positioner and the suspension mechanism, with respect to a seek direction of the head slider.
FIG. 1 is a schematic plan view illustrating three types A, B, and C of positional relationships or the relative arrangements between each head positioner and the relevant suspension mechanism with respect to a disk rotating around its center Q.
The arrangement A is referred to as of the linear type. A rigid arm 2 of a head positioner 1 is moved forward and rearward, namely reciprocally, in a seek direction 3 shown by a two headed arrow, transferring a load beam and a head slider in the seek direction 3 with respect to a disk 12.
The arrangement B is referred to as of the swinging type. A head positioner 4 is rotatable clockwise and counter-clockwise as shown by a double-arrow headed arc, swinging an arm 5. Thus, the relevant head slider suspended by a load beam 13 is transferred over the disk 12 along an arc, namely in a seek direction 6. Hereby, the axial line of the load beam 13 is taken normal to that of the arm 5.
The arrangement C is also referred to as of the swinging type. A head positioner 8 is rotatable clockwise and counter-clockwise, swinging an arm 7 and a load beam 9. Thus the relevant head slider 10 is transferred in a seek direction 11 with respect to the disk 12. Hereby, the longitudinal lines of the load beam 9 and the arm 7 are aligned. As is apparent from the figure, the seek directions 3, 6 and 11 are substantially in the radial direction of the magnetic disk 12.
The linear type arrangement A requires a wide space and reciprocal motion of the head positioner, being rather unsuitable for miniaturizing the associated structure. The arrangements B and C, therefore, are preferably used in a compact type magnetic disk apparatus. However, the head positioner 4 of swinging type B needs a relatively long arm 5, enhancing the rotating inertia moment of the arm 5, which leads to adversely affecting the high speed operation of the magnetic disk apparatus. Consequently, the head positioner 8 of the arrangement C becomes increasingly adopted in a compact and high speed magnetic disk apparatus in recent days. In the present invention, a suspension mechanism for a head slider used in a head positioner of the arrangement C is primarily described.
Now a suspension mechanism for a head slider is described. The head slider is flexibly supported by a suspension mechanism. A typical suspension mechanism, referred to as a Whitney type suspension mechanism, is disclosed in the U.S. Pat. Nos. 3,931,641, published on Jan. 6, 1976, and 4,167,765. published on Sep. 11, 1979, both issued to Watrous. The suspension mechanism of the later have a combined load beam comprising a holding section, a resilient spring section and a substantially rigid section connected to the spring section at one end. At the other end of the rigid section of the load beam, there is fixed a substantially rectangular flexure member having a central finger. A head slider is fixed to the central finger, engaging a rotating magnetic disk with a predetermined spacing therebetween. The spacing is maintained by balancing aerodynamic force provided by an air flow caused by the rotating disk with the resilient force loaded by the relevant load beam. The above described Whitney type is also referred to as a Watrous type, and the flexure member is usually referred to as a gimbal spring.
FIG. 2(a) and FIG. 2(b) are a partial plan view and a side view of a Whitney type suspension mechanism. The whole structure of the suspension mechanism is the same as that described above. A spring member 21, usually referred to as a gimbal spring, is welded to the end portion of a two sided flanged rigid portion 20 of the associated load beam at four points 23 positioned at a supporting portion 21a of the gimbal spring 21. A magnetic transducer 22 (illustrated with chain lines) is fixed to a tongue-like or finger-like central section 21b of the gimbal spring 21. As apparently seen from FIG. 2(a), the central section 21b is connected to a cross leg 21c, being supported in a cantilever suspension, and extending in the longitudinal direction of the load beam. When the head slider of transducer 22 is moved in a seek direction 25 shown by an arrow 25, namely in the direction of the longitudinal center line of the load beam, or in the longitudinal direction of the central section 21b, the mechanical vibration characteristics of the gimbal spring 21 have proved to be favorable for stable seek operation of the transducer 22. When the seek operation is taken in a direction 26 normal to the direction 25, or normal to the longitudinal line of the central section 21b, the mechanical vibration characteristic is substantially unfavorable. This is basically attributed to a low resonant frequency of the gimbal spring 21 in the seek direction 26. The gimbal spring 21 should be designed to have a high resonant frequency in the seek direction since, in general, a low frequency resonant vibration of the gimbal spring 21 is accompanied by rather larger vibration amplitude, and a high frequency resonant vibration with favorably smaller amplitude.
We have performed a computer simulation with regard to mechanical vibration applied to a gimbal spring. There are provided diagrams representing vibration modes of gimbal springs of various types. FIG. 3 is a diagram representing a simulated vibration mode of the gimbal spring of FIG. 2(a) in a seek direction 25 which is in parallel with the longitudinal direction of the central section 21b. The resonant frequency is approximately 37 kHz, sufficiently high to obtain a stable floating movement of the head slider 21 over the relevant rotating disk in a seek direction. FIG. 4 is a diagram of the same in a seek direction 26 which is normal to the longitudinal direction of the central section 21b. The resonant frequency is approximately 5 kHz, unfavorably low causing an unstable seek operation of the head slider 21. In both diagrams, small circles denote the points distributed over the relevant simulated gimbal spring which is deformed by vibration, and underlying dotted figures denote original positions of the corresponding points of the gimbal spring subjected to no vibration. The points 27 and 28 indicate the points at which the central section is fixed to a load beam, and to a head slider respectively.
Consequently, the gimbal spring 21 of FIG. 2(a) is applicable to a suspension mechanism of a recording apparatus having a swinging head positioner disposed in the arrangement B as shown in FIG. 1, whereby a stable movement of the head slider in floating during a seek operation is assured since the seek direction 6 corresponds to the direction 25 of FIG. 2(a). While, the gimbal spring 21 is not applicable to the suspension mechanism of the arrangement C, since the relevant head slider is transferred in the direction 11 which corresponds to the direction 26 of FIG. 2(a). As previously described, the arrangement C is most suitable for a compact and high speed magnetic recording apparatus. An improved gimbal spring suitable for seek operation in all directions has been needed in the art.
Of course, it may be considered that the problem of unstable movement of the head slider during the seek operation might be solved by horizontally turning the direction of the gimbal spring 21 shown in FIG. 2(a) by a right angle with respect to the load beam 20. However, this idea is not practical because of the small area of a portion of the load beam 20 in the vicinity of the free end of the load beam 20 and the resulting asymmetrical structure of the load beam-gimbal spring assembly.